\begin{tikzpicture}
    \pgfmathsetmacro{\R}{1.5}

    \tkzDefPoints{0/0/O}
    \tkzDefPoint(180:\R){A}
    \tkzDefPoint(0:\R){B}
    \tkzDefPoint(270:\R){m}

    \tkzDrawSegment[very thick](A,B)
    \tkzDrawArc[very thick, pattern={mylines[angle=55, distance={4pt}]}](O,A)(B)
    \tkzDrawArc[dashed](O,B)(A)
    \tkzDrawPoint(O)

    \tkzLabelPoints[above](O)
    \tkzLabelPoints[below](m)
    \tkzLabelPoints[left=.3em](A)
    \tkzLabelPoints[right=.3em](B)
\end{tikzpicture}

